Indacaterol maleate is a beta-selective adrenoceptor agonist with potent bronchodilator activity. Indacaterol is chemically known as 5-[(R)-2-(5,6-diethyl-indan-2-yl amino)-1-hydroxy-ethyl]-8-hydroxy-(1H)-quinolin-2-one.
U.S. Pat. No. 7,534,890 claims a process to prepare 5-[(R)-2-(5,6-diethyl-indan-2-ylamino)-1-hydroxy-ethyl]-8-hydroxy-(1H)-quinolin-2-one salt. One of the key steps in the process is reacting an epoxide, such as 8-substituted oxy-5-(R)-oxiranyl-(1H)-quinoline-2-one [Formula (I)] with an amine, such as 2-amino-(5,6-diethyl)-indan to form an intermediate 5-[(R)-2-(5,6-diethyl-indan-2-ylamino)-1-hydroxy-ethyl]-8-substituted oxy-(1H)-quinolin-2-one [Formula (IIa)].

The drawback of this process is opening of epoxide ring is not regioselective and thereby resulting, in formation of substantial quantities of impurities as by products, Formula (IIb) and Formula (IIc) resulting in overall lower yields. The quantity of 2-amino-(5,6-diethyl)-indan used in this step is also large excess than theoretical amounts. Subsequent improvements also did not address this problem effectively.
WO 2013/132514 discloses a process to prepare Indacaterol involving the steps of treating a compound of Formula (III), wherein L is a leaving group, with the amine, 2-amino-(5,6-diethyl)-indan or its acid addition salts to obtain a compound of Formula (IV) or its acid addition salts.

Though higher yields have been claimed, the process has not overcome completely all the problems mentioned earlier.
There is a need for developing a more efficient process for preparing Indacaterol or salts thereof especially for large scale production with higher yields.